Green manure application improves rice growth and urea nitrogen use efficiency assessed using sup(15)N labeling
Meng, X. ((Chinese Academy of Sciences, Xiamen (People's Republic of China). Institute of Urban Environment, Key Laboratory of Urban Environment and Health), (University of Chinese Academy of Sciences, Beijing (People's Republic of China))) | Li, Y. | Zhang, Y. | Yao, H.
Green manure is an efficient nitrogen (N) source when used as an alternative to chemical fertilizer. However, the N taken up by rice derived from green manure, chemical fertilizers or soil native N in complex nutrient systems is unclear. A pot experiment with partial substitution of urea with Chinese milk vetch (a green manure) implemented with 15N-labeled urea and Chinese milk vetch was set up to study the sources of N in rice and the fate of the fertilizers. The dry weights, N contents, N uptake, and urea N use efficiency were notably higher (by 15-16%, 4-13%, 22-30% and 182%-203%, respectively) in the Chinese milk vetch applied with urea treatment than in the urea alone treatment. The uptake of N from Chinese milk vetch and the use efficiency of Chinese milk vetch N were increased with reductions in the urea input amount. The application of Chinese milk vetch substantially changed the fate of urea: higher amounts of urea N were taken up by rice (approximately 29%) and remained as residue in the soil (approximately 15%) in the related treatments than in the treatment with urea alone (10% and 9%). More urea N than Chinese milk vetch N was taken up by rice (29% vs 20%, respectively) and lost (56% vs 14%, respectively), but less urea N than Chinese milk vetch N remained as residue in the soil (15% vs 66%, respectively). The partial substitution of chemical fertilizer with green manure is an effective method of promoting rice growth by supplying N for rice uptake and promoting more efficient N use.
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